The present invention relates to ice hole drilling equipment, and in particular to an ice hole drilling method and apparatus for forming an inverted cone at the bottom of a hole bored through an ice sheet.
Ice augers are well known in the art for drilling holes through the ice for ice fishing. A typical ice auger has one or more boring blades at the lower end of upright drive shank which has a spiral flighting along the lower portion thereof. The drive shank is rotated by manual or power means adjacent its upper end to cut down through the ice similar to the manner in which an old-fashioned hand-operated brace and bit bores a hole though wood. A typical ice auger hole is four to ten inches in diameter.
When landing either a small or large fish through the straight vertical cylindrical bored hole in the ice after the fish is hooked on a fisherman's line, the line must often take on a substantial right angle bend over the jagged edge of the ice at the bottom of the hole. Also, even if the line does not break under this strain in rough action, when the head of the hooked fish comes up against the flat ice surface adjacent the hole, the shock can oftened break the line. When the fish's head does hit the ice in that manner, the fisherman must relax the tension on the line instantaneously to allow the fish's head to move into alignment with the cylindrical hole before pulling up on the line. This instantaneous pressure release will, many times, result in the fish being able to "throw" the hook from its mouth, or this lack of pressure on the line will allow the hook to otherwise become disengaged from the fish.
Separate tools and modifications to ice augers have been proposed in order to form inverted funnel-like bottom openings to the cylindrical ice fishing hole. Typically, such tools were separate from the ice auger itself, or required significant modification to the basic structure of an ice auger.